ONIVEBSITY  OF  CALIFORNIA  FPBLICATIONS 

COLLEGE  OF  AGRICULTURE 
AGRICULTURAL  EXPERIMENT  STATION 

BERKELEY,  CALIFORNIA 


CONTROL  OF  THE  POCKET 
GOPHER  IN   CALIFORNIA 


I.  Natural  History  of  the  Pocket  Gopher; 

Various  Methods  of  Control 

By  JOSEPH  DIXON 

Contribution  from  the  Museum  of  Vertebrate  Zoology 
University  of  California 

II.  A  Method  of  Poisoning  Pocket  Gophers 

By  E.  RALPH  DE  ONG 
Agricultural  Experiment  Station,  University  of  California 


BULLETIN  No.  281 

JULY,  1917 


UNIVERSITY  OF  CALIFORNIA  PRESS 
BERKELEY 

1917 


Benjamin  Ide  Wheeler,  President  of  the  University. 

EXPERIMENT  STATION  STAFF 
HEADS   or  DIVISIONS 

Thomas  Forsyth  Hunt,  Director. 

Edward  J.   Wickson,  Horticulture    (Emeritus). 

Herbert  J.  Webber,  Director  Citrus  Experiment  Station ;   Plant  Breeding. 

Hubert  E.  Van  Norman,  Vice-Director;  Dairy  Management. 

William  A.   Setchell,  Botany. 

Myer  E.  Jaffa,  Nutrition. 
*Robert  H.  Loughridge,  Soil  Chemistry  and  Physics  (Emeritus). 

Charles  W.  Woodworth,  Entomology. 

Ralph  E.  Smith,  Plant  Pathology. 

J.  Eliot  Coit,  Citriculture. 

John  W.  Gilmore,  Agronomy. 

Charles  F.  Shaw,  Soil  Technology. 

John  W.  Gregg,  Landscape  Gardening  and  Floriculture. 

Frederic  T.  Bioletti,  Viticulture  and  Enology. 

Warren  T.  Clarke,  Agricultural  Extension. 

John  S.  Burd,  Agricultural  Chemistry. 

Charles  B.  Lipman,  Soil  Chemistry  and  Bacteriology. 

Clarence  M.  Haring,  Veterinary  Science  and  Bacteriology. 

Ernest  B.  Babcock,  Genetics. 

Gordon  H.  True,  Animal  Husbandry. 

James  T.  Barrett,  Plant  Pathology. 

Fritz  W.  Woll,  Animal  Nutrition. 

Walter  Mulford,  Forestry. 

W.  P.  Kelley,  Agricultural  Chemistry. 

H.  J.  Quayle,  Entomology. 

Elwood  Mead,  Rural  Institutions. 

J.  B.  Davidson,  Agricultural  Engineering. 

H.  S.  Reed,  Plant  Physiology. 

D.  T.  Mason,  Forestry. 

W.  L.  Howard,  Pomology. 

William  G.  Hummel,  Agricultural  Education. 

John  E.  Dougherty,  Poultry  Husbandry. 

S.  S.  Rogers,  Olericulture. 
fFRANK  Adams,  Irrigation  Investigations. 

C.  L.  Roadhouse,  Dairy  Industry. 

David  N.  Morgan,  Assistant  to  the  Director. 

Mrs.  D.  L.  Bunnell,  Librarian. 

Division  of  Entomology 
C.  W.  Woodworth  G.  P.  Gray 

W.  B.  Herms  G.  A.  Coleman 

E.  C.  Van  Dyke  S.  B.  Freeborn 

J.  C.  Bradley  H.  H.  Severin 

E.  O.  Essig  E.  R.  deOng 


*  Died  July  1,  1917. 

t  In  co-operation  with  office  of  Public  Roads  and  Rural  Engineering,   U. 
Department  of  Agriculture. 


I.     NATURAL  HISTORY  OF  THE  POCKET  GOPHER 
VARIOUS  METHODS  OF  CONTROL 

By  JOSEPH  DIXON 
Contribution  from  the  Museum  of  Vertebrate  Zoology,  University  of   California 


The  damage  done  by  the  pocket  gopher  in  the  United  States  has 
been  estimated  at  over  twelve  million  dollars  per  year.1  California 
is  one  of  the  chief  losers.  The  depredations  by  the  gopher  are  locally 
numerous,  involve  nearly  the  entire  state,  and  go  on  all  the  year.  The 
losses,  taken  one  by  one,  may  be  trivial,  but  in  the  aggregate  are 
considerable.  These  features  all  taken  into  account  lead  to  the  belief 
that  more  damage  is  done  by  the  gopher  in  this  state  than  by  any 
other  one  animal,  not  excepting  the  ground  squirrel  or  the  coyote. 

NATURE  OF  THE  POCKET  GOPHER 

The  pocket  gopher  is  a  small,  chunky,  short-legged,  burrowing 
rodent,  with  large  protruding  front  teeth,  fur-lined  cheek  pouches, 
which  are  used  to  carry  food,  not  dirt,  and  which  open  outside  the 
mouth,  small  ears  and  eyes,  and  short  tail,  often  naked  at  the  tip. 
The  gopher  averages  smaller  than  either  the  common  house  rat  or  the 
wood  or  "trade"  rat,  but  there  are  often  great  differences  in  size, 
especially  between  the  sexes.  Because  most  of  the  gopher's  work  is 
done  in  the  dark,  either  underground  or  at  night,  the  disastrous 
results  are  better  known  to  most  people  than  is  the  animal  itself. 

The  Pocket  Gopher  Compared  with  Animals  Sometimes  Mistaken  for  it 


Tail 

Fur 

External  cheek 
pouches 

Front  teeth 

Gopher 

short,  2  to  3  in., 
often  naked  at  tip 

harsh 

always  present 

large,  protruding 

Mole 

short,  1  to   1%  in. 

velvety 

none 

small 

Meadow  mouse 

short,  1  to  1%  in. 

harsh 

none 

small 

Kangaroo  rat 

long,  6  to  10  in. 

silky 

always  present 

small 

The  mistake  most  often  made  is  that  of  confusing  the  work  of  the 
mole  with  that  of  the  gopher.  These  two  animals,  however,  are  totally 
different.  The  mole  is  not  a  rodent  (gnawer)  at  all.  It  lives  on 
animal  matter  (worms,  grubs,  and  insects)  and  not  vegetable  matter. 
A  mole  may  occasionally  be  caught  in  a  gopher  run;  but  the  gopher 


iU.  S.  Dept.  Agric,  Farmers  Bulletin  No.  335   (1908),  p.  19. 


4  UNIVERSITY  OF   CALIFORNIA EXPERIMENT  STATION 

is  the  real  cause  of  such  damage  as  eating  potatoes  and  cutting  off 
roots,  which  is  sometimes  attributed  to  the  mole.  The  mole  crowds 
along  just  beneath  the  surface  in  loose  soil,  leaving  ridges  in  which 
numerous  cracks  are  visible.  The  gopher  digs  tunnels,  and  the  sides 
of  these  are  left  clean  cut.  During  dry  weather,  especially,  the  mole 
often  burrows  deeply  and  throws  up  mounds,  but  these  show  no  trace 
of  an  opening,  while  those  of  the  gopher  do.  Many  moles  have  been 
caught  for  museum  specimens  by  setting  Macabee  gopher  traps  care- 
fully in  the  main  runs  of  moles  (see  p.  9,  Special  Sets). 

BREEDING    HABITS 

The  data  recorded  with  the  2100  specimens  of  gophers,  collected 
throughout  the  state,  which  are  now  in  the  University  of  California 
Museum  of  Vertebrate  Zoology,  form  the  main  basis  for  the  following 
breeding  notes.  Gophers  have  from  three  to  twelve  young  in  a  litter. 
The  smallest  number  of  embryos  (unborn  young)  found  in  females 
were  three  and  four,  the  greatest  eleven  and  twelve,  while  the  average 
in  twenty-eight  females  from  many  parts  of  the  state  was  5.8.  There 
is  evidence  to  indicate  that  two  litters  are  frequently  raised  in  a 
season  where  food  is  plentiful,  as  in  alfalfa  fields. 

Out  of  eighteen  female  gophers  taken  near  San  Bernardino, 
November  7  and  8,  1916,  four  contained  small  embryos  and  all  but 
two  of  the  remainder  were  ready  to  breed.  The  breeding  season  can 
perhaps  best  be  gauged  by  the  period  of  growth  of  the  alfilaria,  or 
"filaree. "  This  and  malva,  among  all  our  native  plants,  seem  to  be 
the  gopher's  favorite  food.  The  alfilaria  is  one  of  the  earliest  plants 
to  start  after  the  first  fall  rains,  and  the  resulting  nutritious  food 
supply  seems  to  start  the  gophers  breeding.  The  nest  is  underground, 
and  usually  placed  beneath  a  stump,  rock  pile,  brush  pile,  or  some 
other  such  surface  protection  as  will  discourage  badgers  or  coyotes 
from  digging.  The  young  remain  in  it  for  several  weeks  after  birth 
and  do  not  leave  until  they  are  nearly  half  grown,  when  they  are  able 
to  forage  for  themselves.  In  plowing  an  abandoned  field  in  San 
Diego  County  in  the  middle  of  January,  1911,  the  writer  uncovered 
at  the  bottom  of  the  furrow  near  a  willow  stump  a  nest  containing 
a  mother  gopher  and  four  hairless,  helpless  young,  barely  able  to 
crawl.  ' 

The  following  dates  show  the  approximate  time  of  year  when  the 
main  crop  of  young  begin  leaving  the  nest,  though  young  may  also 
be  found  foraging  for  themselves  much  earlier  or  later  than  these 
dates:  southern  California,  March  30:  San  Joaquin  and  Sacramento 


CONTROL   OF   THE   POCKET   GOPHER   IN    CALIFORNIA  0 

valleys,  April  1;  Owens  Valley,  April  15;  foothills  of  Sierra  Nevada, 
April  30;  northwest  coast  region,  May  15. 

WHEN  TO  TRAP  AND  POISON 

Obviously,  the  time  to  combat  gophers  most  successfully  is  before 
the  young  make  their  appearance  in  the  spring.  Poisoning  is  very 
effective,  but  harder  to  carry  on  than  trapping  in  the  dry  season, 
especially  during  August,  September,  and  October,  when  the  supply 
of  green  food  is  scarcest.  Trapping  is  most  easily  carried  on  soon 
after  the  green  vegetation  starts  in  the  early  winter  or  spring,  for 
the  gophers  are  then  most  active.  The  wise  old  males  which  usually 
cause  the  trapper  the  most  trouble,  seem  to  lose  their  instinctive 
caution  during  the  mating  season  and  often  blunder  blindly  into 
traps  which  they  would  never  enter  at  other  times.  Every  female 
caught  at  this  time,  before  the  young  are  born,  means  the  destruction 
of  from  four  to  twelve  gophers  for  the  current  season. 

METHODS  OF   DESTRUCTION 

The  five  most  effective  methods  of  destroying  gophers  are:  (1) 
poisoning  with  strychnine;  (2)  trapping;  (3)  fumigation  with  carbon 
bisulphide;  (4)  flooding;  (5)  for  permanent  relief,  encouragement 
and  protection  of  the  gopher's  natural  enemies,  especially  the  barn 
owl  and  gopher  snake. 

The  solution  of  the  gopher  problem  lies  in  a  combination  of  two 
or  more  of  the  above  methods,  rather  than  in  any  one  of  them.  Where 
a  large  acreage  is  to  be  treated,  poisoning  with  strychnine  will  be 
found  effective  in  reducing  the  pest.  Traps  are  safe,  can  be  used  at 
any  time,  and  are  effective  in  the  hands  of  a  man  who  is  not  afraid 
to  dig  and  who  uses  care  in  setting  and  in  placing  his  traps.  Traps 
are  especially  adapted  to  pasture,  where  there  might  be  danger  of 
poisoning  stock,  to  gardens,  to  orchards  and  to  banks  of  irrigation 
ditches.  The  use  of  carbon-bisulphide  should  be  restricted  to  periods 
when  the  ground  is  wet.  Both  traps  and  carbon-bisulphide  are  good 
"follow-up"  methods  in  getting  the  gophers  which  refuse  to  take 
poisoned  bait.  Land  that  can  be  successfully  flooded,  so  as  to  drown 
out  the  gophers,  has  usually  been  graded  for  irrigated  crops  such  as 
alfalfa.  Flooding  (irrigation)  is  therefore  automatic,  and  I  have 
yet  to  see  anyone  who  was  so  stupid  that  he  would  not  hunt  and  kill 
gophers  which  were  being  drowned  out.  A  man  that  kills  all  the 
gopher  snakes  and  barn  owls  on  his  place  will  have  to  fight  gophers, 
nnd  deservedly  so. 


6  UNIVERSITY  OF   CALIFORNIA EXPERIMENT  STATION 

1.  POISONING 

The  four  things  necessary  to  poison  gophers  successfully  are:  (a) 
an  effective  poison  such  as  strychnine;  (6)  a  succulent  bait  that  will 
be  relished  by  the  gopher;  (c)  bait  large  enough  so  that  the  gopher 
must  eat  it  at  once  and  not  put  it  in  his  pocket  and  carry  it  away  to 
his  storehouse;  and  (d)  placing  of  the  bait  in  the  main  run  where  the 
gopher  can  readily  find  it  and  not  cast  it  out  with  the  dirt,  as  would 
often  be  the  case  were  it  placed  in  an  open  hole  or  in  a  lateral. 

In  poisoning  ground  squirrels  it  has  been  found  that  strychnine  is 
more  readily  absorbed  through  the  membranous  cheek  pouches,  which 
open  inside  the  mouth,  than  through  the  stomach.  However,  the  fur- 
lined  pockets  of  the  gopher  which  open  outside  the  mouth  do  not 
readily  absorb  the  strychnine.  Hence  poisoned  bait,  such  as  strych- 
nine-coated barley,  which  is  effective  on  the  ground  squirrel,  is  not 
effective  on  the  gopher.  The  gopher  often  puts  the  poisoned  grain 
in  its  pockets  and  carries  it  away  to  the  storehouse,  where  the  poison 
soon  loses  strength. 

There  are  two  methods  of  using  strychnine.  The  first  method, 
which  is  adapted  to  treating  a  large  acreage,  is  given  by  Mr.  de  Ong 
in  the  second  part  of  this  bulletin.  This  method  of  placing  the  bait 
in  the  run  through  a  hole  made  by  a  probe  works  well  when  the  soil 
is  damp.  However,  in  cultivated  fields  when  the  ground  is  dry,  a 
second  method  becomes  necessary,  as  the  dry  surface  soil  will  run  in 
and  promptly  fill  up  the  hole  made  by  the  probe.  In  this  case  it  is 
best  to  dig  down  and  place  the  poisoned  bait  well  back  in  the  main 
run  of  the  gopher.  Many  times  only  a  few  poisoned  baits  are  re- 
quired.     These  may  be  prepared  quickly  and  used  as  follows : 

Carrots,  parsnips,  sugar  beets  or  sweet  potatoes,  cut  into  one-inch 
cubes  and  poisoned  by  inserting  a  few  sulphate  of  strychnine  crystals 
into  a  slit  made  by  the  point  of  a  knife,  are  good,  especially  in  the 
dry  season  when  green  food  is  scarce.  Carry  the  poisoned  cubes 
in  an  old  covered  pail  marked  Poison.  Find  the  main  run  in  the 
same  manner  as  when  setting  a  trap,  and  with  a  slender  pointed  stick, 
so  that  you  will  not  have  to  touch  the  bait,  place  one  of  the  poisoned 
cubes  a  foot  back  in  each  hole,  which  should  then  be  tightly  closed. 
The  hole  may  be  opened  forty-eight  hours  later  and  if  it  remains  open 
the  gopher  may  be  considered  dead. 

Poisoned  alfalfa  has  been  found  effective  in  orange  groves  in 
southern  California.  The  heads  of  a  few  tender  stalks  are  bent 
back  and  tied  with  a  string  so  that  the  tuft  is  formed  at  the  end.  A 
little  strychnine  mixed  with  orange  juice  is  concealed  inside  the  tuft, 


CONTROL   OF    THE   POCKET   GOPHER   IN    CALIFORNIA  7 

which  is  then  pushed  well  back  in  the  run,  and  the  hole  then  tightly 
covered. 

2.  TKAPPING 

Almost  any  kind  of  trap  will  catch  gophers  sometimes,  a  few  will 
catch  gophers  most  of  the  time,  but  we  have  yet  to  see  the  trap  that 
will  catch  every  gopher  every  time.  There  seems  to  be  among  experi- 
enced farmers  throughout  the  state  a  decided  preference  for  a  gopher 
trap  of  the  Macabee  type  (fig.  2a).  After  a  practical  test  in  the  field, 
extending  over  several  years,  the  "catching  average"  of  this  style  of 
trap  has  been  found  to  equal  or  surpass  that  of  any  other  trap  that 
the  writer  has  been  able  to  secure.  Its  cheapness,  compactness,  and 
reliability  place  it  at  the  head  of  the  list. 

Any  form  of  explosive  trap,  or  "gopher-gun,"  is  not  recommended 
because  of  the  degree  of  danger  which  attends  its  use. 

Where  to  Set  the  Traps 

The  most  effective  "set"  for  the  Macabee  trap  is  in  the  main 
runway  (fig.  la),  and  not  in  the  lateral  run  (fig.  lb)  that  leads  to 
the  surface  mound.  This  necessitates  the  use  of  two  traps  per  setting, 
one  in  each  direction;  but  the  results  are  so  much  more  certain  and 
quicker  that  the  catch  per  trap  per  day  is*  greater  than  where  but 
one  trap  is  set  in  a  lateral  run,  where  it  is  often  filled  full  of  dirt  by 
the  gopher.  A  common  stiff-handled  twelve-inch  iron  spoon  is  of 
great  assistance  in  finding  the  main  run  and  in  properly  placing  the 
trap.  This  spoon  had  better  be  supplemented  by  a  light  short- 
handled  shovel,  for  the  man  that  is  afraid  to  dig  will  never  get  rid 
of  his  gophers.  The  freshest  mound  should  be  selected  and  the 
probable  direction  of  the  main  run  determined  by  noting  the  angle 
of  the  dirt-plugged  hole.  The  mounds  are  usually  situated  one  or 
two  feet  distant  from,  and  nearly  at  right  angles  to,  the  main  run. 

Now  to  business :  Take  the  bowl  of  the  iron  spoon  in  your  hand 
and  push  the  other  (handle)  end  of  the  spoon  into  the  ground  where 
you  think  the  lateral,  which  leads  from  the  mound  to  the  main  run,  is. 
If  the  spoon  strikes  an  open  lateral  you  will  feel  the  spoon  handle 
drop  through  the  opening.  If  the  lateral  is  filled  loosely  with  dirt 
the  drop  will  be  less  noticeable  but  still  plainly  felt.  If  it  is  plugged 
tight  you  will  have  to  use  the  shovel  to  dig  down  a  little  distance 
before  probing  again.  If  this  fails,  try  a  new  mound.  When  the 
lateral  is  found,  follow  it  down  to  the  main  run,  which  is  always  kept 
open  by  the  gopher.  Use  the  shovel  until  you  have  cleared  a  place 
where  you  can  set  a  trap  in  each  direction.     Smooth  out  the  hole  with 


s 


UNIVERSITY  OF   CALIFORNIA EXPERIMENT  STATION 


the  spoon  but  do  not  disturb  more  than  is  necessary.  Set  the  treadle, 
or  pan,  so  that  a  slight  touch  will  spring  the  trap,  and  place  the  trap 
well  back  within  the  hole.  A  little  loose  dirt  should  be  left  in  the 
bottom  of  the  hole,  as  it  will  cover  the  prongs  and  front  end  of  the 
trap  when  the  trap  is  pushed  into  place.  When  in  place,  press  the 
trap  down  firmly  so  that  it  will  not  slide  back  if  the  gopher  pushes 
against  it.  Then  plug  the  burrow  with  a  clod  or  a  handful  of  grass 
or  alfalfa  and  cover  completely  so  that  no  light  can  get  to  the  trap. 
A  gopher's  instinct  prompts  him  to  tightly  close  all  open  burrows  to 
keep  out  his  natural  enemy,  the  gopher  snake   (nature's  own  gopher 


Fig.  1. — a.  Best  place  to  set  traps  or  leave  poisoned  bait,  in  the  main  run 
which  is  always  kept  open  by  the  gopher,  b.  Lateral  run,  usually  partly  plugged 
with  dirt,  leading  to  surface  mound. 


trap).  Therefore,  if  poisoned  bait  or  a  trap  be  placed  in  an  open  hole, 
or  the  hole  be  left  open,  the  poisoned  bait  will  often  be  thrown  out, 
to  become  a  menace  to  stock,  or  the  trap  sprung  by  the  dirt  which  the 
gopher  pushes  ahead  of  him  in  plugging  the  open  hole.  Set  the  traps 
and  place  the  poisoned  bait  well  back  in  the  main  runs,  which  should 
then  be  tightly  closed. 

The  trap  should  have  a  wire  or  light  chain  attached  to  it  and 
fastened  to  a  chunk  of  stove-wood  or,  better  still,  an  old  worn-out 
stewpan  which  will  rattle  should  you  forget  and  run  over  the  set 
trap  with  a  harrow  or  cultivator.  Coyotes  and  house-cats  dislike  the 
noise,  also,  and  do  not  drag  the  trap  so  far  when  they  rob  it.  In  case 
only  one  trap  is  available  when  the  main  run  is  found,  a  careful  watch 
will  often,  but  not  always,  reveal  one  or  more  little  flies  emerging  from 
the  run  where  it  is  first  opened.      These  flies  seem  to  have  a  direct 


CONTROL    OF    THE   POCKET   GOPHER   IN    CALIFORNIA  9 

relation  to  the  gopher,  as  experiments  have  shown  that  the  side  that 
they  come  from  is  the  one  occupied  at  that  time  by  the  gopher  and 
hence  the  place  to  set  the  trap.  Traps  should  be  visited  morning  and 
evening,  or  oftener. 

Special  Sets 

Individual  gophers  will  frequently  be  found  that  refuse  to  enter 

any  sort  of  trap.     These  gophers  are  generally  old  males  and  are  likely 

to  be  the  ones  that  do  most  of  the  gnawing  on  fruit  trees.      When 

one  of  these  old-timers  repeatedly  fills  the  trap  with  dirt,  then  special 


Fig.  2. — a.  Eegular  Macabee  gopher  trap.     ~b.  Reconstructed  Macabee  trap  used  to 
catch  ' '  wise ' '  gophers,  and  moles. 

care  becomes  necessary  to  catch  him.  Moles  may  be  captured  in  this 
way  also.  Take  a  Macabee  trap  (fig.  2a)  and  move  the  treadle 
forward  about  an  inch  and  a  half,  placing  the  wire  which  carries 
the  treadle  below,  instead  of  above  the  two  longitudinal  wires.  Cut 
off  the  wire  trigger  to  meet  this  change  (fig.  2b).  Then  bend  the 
treadle  backwards  at  right  angles  to  its  former  position  (fig.  3a)  so 
that  it  will  lie  parallel  with  the  trap  (fig.  3c),  instead  of  sticking  up 
at  right  angles  and  obstructing  the  runway  (as  in  fig.  36).  Set  the 
trap  so  it  will  spring  easily.  Put  a  pinch  of  loose  cotton  under  the 
treadle  to  keep  the  dirt  out,  and  when  the  trap  has  been  placed  in 


10 


UNIVERSITY  OF   CALIFORNIA EXPERIMENT  STATION 


the  run  take  a  stick  and  cover  the  whole  trap  with  a  thin  layer  of  loose 
dirt.  Another  method  is  to  take  a  recently  caught  female  and  rub 
the  reproductive  parts  on  the  face  of  the  treadle  of  the  regular 
Macabee  trap.  A  few  drops  of  urine  may  be  squeezed  out  during  the 
process,  but  this  only  adds  to  the  efficacy  of  the  decoy.  If  all  else 
fails  catch  a  gopher  snake  and  turn  him  loose  in  the  run. 

After  you  have  put  in  poison  or  traps  the  tops  of  all  the  gopher 
mounds  should  be  kicked  off,  so  that  when  you  make  your  next  round 
the  newly  made  mounds  will  tell  you  where  gophers  remain  and  where 
to  put  out  more  poison  or  traps. 

The  reconstructed  form  of  the  Macabee  trap  above  described  will 
be  furnished  by  the  manufacturer  if  the  demand  warrants. 


.1 

1             / 

o 

i=fl 

(L 

__.             _                      >w/_               ^ 

a                                   be 

Fig.  3. — a,  b.  Vertical  " treadle' '  or  "pan"  of  regular  trap;  heavy  dotted  lines 
show  places  to  bend  vertical  treadle  to  form  horizontal  treadle  (e). 


3.  CAEBON  BISULPHIDE 

Carbon  bisulphide  is  volatile  as  well  as  inflammable  and  the  gas 
from  it  is  explosive,  so  that  caution  should  attend  its  use.  Its  use 
is  advisable  only  when  the  ground  is  damp  or  full  of  water,  as 
the  cracks  in  dry  ground  let  the  gas  escape.  It  does  not  seem  to  be 
as  effective  on  gophers  as  on  ground  squirrels,  for  the  gopher  burrows 
are  much  more  extensive  and  the  gopher  is  therefore  harder  to  reach. 
It  is  more  valuable  as  a  "follow  up"  method  than  for  general  appli- 
cation. 

There  are  two  methods  of  applying  carbon  bisulphide.  The  first 
is  to  pour  about  a  tablespoonful  on  cotton  waste,  corncobs  or  other 
absorbent  material,  which  is  then  quickly  pushed  down  the  hole  and 
the  opening  promptly  and  tightly  closed.      The  better  way  is  by  the 


CONTROL  OF  THE  POCKET  GOPHER  IN  CALIFORNIA  11 

use  of  a  special  apparatus  which  forces  the  gas  down  the  hole.  This 
is  accomplished  by  a  hand  bellows  attached  to  the  top  of  a  tank  that 
contains  the  carbon  bisulphide.  The  air  is  forced  through  a  pipe  from 
the  bellows  to  the  tank,  where  it  passes  over  the  bisulphide  and  is 
carried  out  through  a  rubber  hose  which  is  pushed  down  the  open  hole 
and  then  tightly  surrounded  by  dirt.  Contrivances  of  this  sort,  such 
as  the  Eureka  Squirrel  Exterminator,  are  on  the  market. 

4.  FLOODING 

As  has  been  pointed  out  above,  flooding  of  fields  often  is  an  essen- 
tial part  of  agriculture  in  irrigated  sections.  The  main  point,  then, 
is  to  see  to  it  that  the  gophers  which  are  drowned  out  and  seek  the 
higher  borders,  are  promptly  dispatched.  A  good  dog  will  do  this 
effectively  until  he  gets  tired,  and  then  the  farmer  must  be  ready  to 
give  the  gophers  proper  attention  with  the  back  of  a  shovel. 

5.  ENCOUEAGEMENT  OF  THE  GOPHER'S  NATURAL  ENEMIES 

Comparatively  few  ranchers  realize  the  true  value  of  barn  owls 
and  gopher  snakes  as  allies  in  their  war  on  gophers.  A  pair  of 
nesting  barn  owls  were  .found  by  the  writer  to  catch  from  three  to 
six  gophers  a  day  for  their  young.  No  one  who  has  ever  counted 
the  number  of  rodents  brought  in  by  a  pair  of  these  owls  during 
a  single  season  would  ever  doubt  their  value  as  gopher  destroyers. 

On  May  13,  1914,  near  Mendota,  Fresno  County,  California,  Mr. 
John  G.  Tyler2  found  two  pairs  of  barn  owls  nesting  in  an  old  tank 
house.  "One  nest  was  placed  in  the  tank  on  the  bones,  fur,  pellets, 
and  refuse  that  had  accumulated  to  a  depth  of  several  inches.  One 
bird  was  perched  on  a  beam  overhead  asleep,  while  his  mate  occupied 
the  nest,  which  contained  four  very  small  birds  and  six  eggs.  Scat- 
tered about  on  the  floor  were  five  pocket  gophers  (Thomomys) ,  five 
kangaroo  rats  {Perodipus),  one  pocket  mouse  (Perognathus),  and  two 
white-footed  mice  (Peromyscus),  all  of  which  were  in  good  condition 
and  undoubtedly  of  the  previous  night's  capture.  Besides  these, 
there  were  partly  eaten  remains  and  fresh  skeletons  of  several  more. 
...  If  the  thoughtless  persons  who  so  relentlessly  destroy  this  owl 
on  account  of  its  supposed  fondness  for  chickens  and  pigeons  would 
take  the  trouble  to  keep  watch  of  a  nest-site  through  one  season,  the 
most  ignorant  among  them  could  hardly  fail  to  realize  that  they  are 
working  against  their  own  best  interests  whenever  they  kill  a  barn 
owl." 


2  Condor,  XVII,  January,  1915,  p.  57. 


12  UNIVERSITY  OF   CALIFORNIA EXPERIMENT  STATION 

The  gopher  or  bull  snake  may  steal  eggs  occasionally,  but  his  main 
diet  consists  of  small  rodents,  chiefty  gophers.  A  wise  man  will  there- 
fore protect  the  gopher  snakes  on  his  premises.  Every  gopher  that 
the  barn  owl  or  gopher  snake  destroys  means  one  less  for  yon  to  oatch. 

OTHER  METHODS  OF  CONTROL 

Some  other  methods  of  controlling  pocket  gophers  are:  (1)  pro- 
tecting trees  with  wire  netting;  (2)  planting  gopher  repellant  plants; 
(3)  using  rodent  virus;  (4)  surrounding  small  plot  by  a  trench;  (5) 
protecting  of  ditches  by  cement. 

1.  PEOTECTING  TREES  WITH  WIRE  NETTING 
One-inch  mesh  galvanized  wire  netting  in  the  form  of  a  cylinder 
one  foot  in  diameter  and  eighteen  inches  high  may  be  placed  about 
young  trees  when  they  are  planted,  to  protect  them  from  the  attacks 
of  gophers.  The  top  of  the  netting  should  be  put  just  below  the 
surface  of  the  ground,  and  the  trunk  of  the  tree  above  ground  pro- 
tected in  some  other  way  so  as  not  to  interfere  with  cultivation,  which 
the  netting  will  certainly  do  if  it  sticks  above  ground. 

2,   3.  GOPHER  REPELLANT   PLANTS;    RODENT   VIRUS 
Plants  which  will  drive  gophers  away,  and  a  virus  of  a  "gopher 
infectious"    disease,    have    both    been   much    exploited,    but    neither 
remedy  seems  to  have  "made  good,"  and  cannot  therefore  be  recom- 
mended. 

4.  SURROUNDING  SMALL  PLOT  BY  A  TRENCH 
Small  plots  of  ground  have  been  protected  by  being  entirely  sur- 
rounded by  a  trench  eighteen  inches  wide  and  two  feet  deep,  with 
open  five-gallon  cans  buried  flush  with  the  bottom  in  the  ditch  at 
twenty-five  foot  intervals,  to  catch  and  hold  the  gophers  which  tumble 
into  the  ditch,  and  thence  into  the  cans. 

5.  PROTECTION  OF  DITCHES  BY  CEMENT 
A  power  company  which  had  much  trouble  with  gophers  in  a  large 
ditch  dug  a  four-inch  trench  six  feet  deep  straight  down  through  the 
middle  of  the  lower  bank  of  the  ditch.  The  dirt  was  loosened  with  an 
iron  bar  and  removed  with  a  narrow  shovel,  of  the  type  used  in  digging 
telephone-pole  holes.  The  trench  was  then  filled  with  a  "lean" 
mixture  of  cement  and  sand,  which  was  carried  on  a  barge  that  floated 
on  the  water  in  the  ditch.      The  cement  was  conveyed  to  the  bottom 


CONTROL    OF    THE   POCKET    GOPHER    IN    CALIFORNIA  13 

of  the  trench  by  a  galvanized  iron  chute  which  was  built  in  sections 
so  as  to  be  readily  adapted  to  any  depth.  This  method  was  said  to 
have  been  expensive,  but  satisfactory  in  the  long  run. 

A  small  irrigation  ditch  having  a  seven-foot  "surface"  has  been 
protected  from  gophers,  weeds  and  leakage  by  applying  to  the  sides 
and  bottom,  first  a  %-inch  coat  of  7  to  1  cement  and  then  a  surface 
layer  %  inch  thick  of  3  to  1  cement.      This  proved  satisfactory. 

All  of  these  preventatives  are  costly  and  are  advisable  only  in 
those  situations  where  protection  against  gophers  cannot  be  obtained 
by  their  destruction. 


14  UNIVERSITY  OF   CALIFORNIA EXPERIMENT   STATION 


II.     A  METHOD  OF  POISONING  POCKET  GOPHERS 

By  E.  EALPH  de  ONG 
Agricultural  Experiment  Station,  University  of  California 


One  of  the  most  satisfactory,  and  at  the  same  time,  one  of  the 
cheapest  methods  of  controlling  pocket  gophers  is  through  the  use  of 
poisoned  baits,  such  as  chopped  vegetables,  dried  prunes,  or  raisins. 
The  formula3  which  has  proved  very  successful  at  the  University  Farm 
is  as  follows : 

Sweet  potatoes,  parsnips,  or  carrots 8  quarts 

Flour  paste  y2  pint 

Strychnine  alkaloid,  powdered y4   ounce 

Saccharine  i/1(.  ounce 

Chop  the  vegetables,  or  cut  them  with  a  knife,  into  one-half  inch 
cubes.     Make  a  thin  paste  of  flour  and  water  and  boil  for  a  few  min- 


Fig.  4. — Tool  for  probing  ground  so  as  to  locate  underground  burrows  of  pocket 

gophers. 

utes.  Stir  the  strychnine  and  saccharine  into  one-half  pint  of  the 
cooked  paste  and  pour  it  over  the  chopped  vegetables,  stirring  until 
each  piece  is  coated.  Two  or  three  or  these  cubes  are  to  be  dropped 
in  each  runway.  The  alkaloid  form  of  strychnine  should  be  used  in 
preference  to  the  sulphate,  as  the  former  is  but  slightly  soluble  in 
water  and  remains  largely  on  the  outside  of  the  bait,  leaving  the 
center  sweet.  The  saccharine  is  used  to  disguise  partially  the  bitter- 
ness of  the  strychnine. 

To  locate  the  underground  burrows,  the  method  previously  recom- 
mended will  prove  satisfactory,  or  a  simple  tool  may  be  used,  which 
can  be  made  at  any  blacksmith  shop.  This  is  a  shank  of  steel,  three- 
quarters  of  an  inch  in  diameter  and  about  fifteen  inches  long,  pointed 

3  U.  S.  Dept.  Agric,  Farmers  Bulletin  No.  484,  p.  39. 


CONTROL  OF  THE  POCKET  GOPHER  IN  CALIFORNIA  15 

at  the  lower  end.  This  is  fitted  into  a  wooden  or  iron  handle,  three 
feet  long,  one  end  tapered  slightly,  to  be  nsed  in  enlarging  the  open- 
ings made  into  the  runway.  To  aid  in  sinking  the  probe  into  the 
ground,  a  foot-piece  should  be  welded  on  to  one  side  of  the  steel  rod 
(fig.  4).  To  use  this  tool  it  is  necessary  for  the  ground  to  be  wet 
down  to  the  ordinary  depth  at  which  the  gophers  are  working,  usually 
from  three  to  eight  inches  below  the  surface.  Sink  the  probe  into  the 
ground,  ten  or  fifteen  inches  from  the  gopher  hill,  continuing  the 
work  until  the  burrow  is  located,  which  will  be  recognized  by  a  sudden 
dropping  of  the  probe.  If  necessary,  enlarge  the  opening  into  the 
runway  with  the  blunt  end  of  the  handle,  then  drop  in  the  bait,  and 
close  the  hole  with  the  foot.  The  operator  will  soon  become  expert  in 
locating  the  runways  so  that,  where  gophers  are  abundant,  one  man 
may  bait  hundreds  of  runs  in  a  single  day.  One  piece,  of  seven  acres 
of  heavily  infested  alfalfa  land,  has  been  covered  by  one  man  in  a 
day  and  a  half. 

Poisoning  is  more  successful  from  late  summer,  after  green  food 
has  become  scarce,  until  grass  starts  in  the  fall  or  winter,  depending 
on  rainfall  and  temperature.  It  should  be  delayed  until  the  top 
layer  of  ground  is  thoroughly  wet,  not  only  to  facilitate  operations, 
but  because,  after  the  heavy  rains  begin,  gophers  have  a  tendency  to 
migrate  into  fence  rows  or  the  uncultivated  strip  along  driveways, 
which  greatly  reduces  the  amount  of  ground  necessary  to  cover.  One 
thorough  application  in  such  places  should  kill  90  per  cent  or  more 
of  the  gophers.  After  another  rain  the  ground  can  be  gone  over 
again  and  any  fresh  hills  poisoned.  Alfalfa  is  not  as  successfully 
treated  as  orchard  or  bare  land,  on  account  of  the  abundance  of  suc- 
culent food. 


STATION    PUBLICATIONS    AV  AIL  ABLE   FOR   FREE    DISTRIBUTION 


REPORTS 

1897.      Resistant  Vines,   their  Selection,   Adaptation,   and  Grafting.     Appendix  to  Viticultural 
Report  for  1896. 

1902.  Report  of  the  Agricultural  Experiment   Station   for   1898-1901. 

1903.  Report  of  the  Agricultural   Experiment   Station   for   1901-03. 

1904.  Twentv-second  Report  of  the  Agricultural   Experiment   Station  for    1903-04. 

1914.  Report  of  the   College  of  Agriculture   and  the  Agricultural   Experiment   Station,    July, 

1913-June,    1914. 

1915.  Report  of  the  College  of  Agriculture  and  the  Agricultural   Experiment   Station,    July, 

1914-June,    1915. 

1916.  Report  of  the   College  of  Agriculture   and  the   Agricultural   Experiment   Station,    July, 

1915-June,    1916. 

BULLETINS 


No. 
207. 
208. 
212. 
213^ 
216. 


2?5. 
230. 
241. 
242. 
244! 
246. 
248. 

249. 
250. 
251. 


°m2. 
253. 


°55. 

257. 


No. 

65. 
69. 
70. 


107. 


108. 
109. 


113. 
114. 
115. 
117. 

118. 
121. 

124. 
126. 
127. 
128. 
129. 
130. 
131. 
132. 
133. 
134. 
135. 
136. 
137. 
138. 
139. 


The  Control  of  the  Argentine  Ant. 

The  Late  Blight  of  Celery. 

California  White  Wheats. 

The  Principles  of  Wine-Making. 

A  Progress  Report  Upon  Soil  and  Cli- 
matic Factors  Influencing  the  Com- 
position of  Wheat. 

Tolerance  of  Encnl  ptus  for  Alkali. 

Enological  Investigations. 

Vine  Pruning  in  California,  Part  I. 

Humus  in  California  Soils. 

Utilization   of  Waste  Oranges. 

Vine  Pruning  in  California,   Part  II. 

The  Economic  Value  of  Pacific  Coast 
Kelps. 

Stock-Poisoning  Plants  of  California. 

The  Loquat. 

Utilization  of  the  Nitrogen  and  Organic 
Matter  in  Septic  and  Imhoff  Tank 
Sludges. 

Deterioration   of  Lumber. 

Irrigation  and  So'l  Conditions  in  the 
Sierra  Nevada  Foothills,  California. 

The   Citricola    Scale. 

New  Dosage  Tables. 


No. 

261.  Melaxuma    of    the    Walnut,     "Juglans 

regia." 

262.  Citrus   Diseases   of   Florida    and   Cuba 

Compared  with  Those  of  California. 

263.  Size  Grade  for  Ripe  Olives. 

264.  The  Calibration  of  the  Leakage  Meter. 

265.  Cottonv  Rot  of  Lemons  in   California. 

266.  A  Spotting  of  Citrus  Fruits  Due  to  the 

Action  of  Oil  Liberated  from  the  Rind. 

267.  Experiments  with  Stocks  for  Citrus. 

268.  Growing  and  Grafting  Olive  Seedlings. 

270.  A  Comparison  of  Annual  Cropping,  Bi- 

ennial Cropping,  and  Green  Manures 
on  the  Yield  of  Wheat. 

271.  Feeding  Dairv  Calves  in  California. 

272.  Commercial  Fertilizers. 

273.  Preliminary  Report  on  Kearney  Vine- 

yard Experimental  Drain. 

274.  The  Common   Honev  Bee  as  an   Agent 

in   Prune   Pollination. 

275.  The  Cultivation  of  Belladonna  in  Cali- 

fornia. 

276.  The  Pomegranate. 

277.  Sudan  Grass. 

278.  Grain   Sorghums. 

279.  Irrigation  of  Rice  in  California. 


The   California    Insecticide   Law. 

The  Extermination  of  Morning-Glor<\ 

Observations  on  the  Status  of  Corn 
Growing   in    California. 

Hot   Room   Callusing. 

The  Common  Ground  Squirrels  of 
California. 

Spraying  Walnut  Trees  for  Blight  and 
Aphis  Control. 

Grape  Juice. 

Communit"  or  Local  Extension  Work 
bv  the  High  School  Agricultural  De- 
partment. 

Correspondence  Courses  in  Agriculture. 

Increasing  the  Dut-  of  Water. 

Grafting  Vinifera  Vine-ards. 

The  Selection  and  Cost  of  a  Small 
Pumping   Plant. 

The  County  Farm  Bureau. 

Some  Things  the  Prospective  Settler 
Should  Know. 

Alfalfa   Silage  for  Fattening  Steers. 

S-nraving  for  the  Grape  Leaf  Hopper. 

House  Fumigation. 

Insecticide  Formulas. 

The  Control  of  Citrus  Insects. 

Cabbage   Growing  in   California. 

Spraving  for  Control  of  Walnut  Aohis. 

When  to  Vaccinate  against  Hog  Cholera, 

Countv   Farm   Adviser. 

Control   of   Raisin    Insects. 

Official  Tests  of  Dairy  Cows. 

Melilot"s   Tndica. 

Wood  Decav  in   Orchard  Trees. 

The  Silo  in  California  Agriculture 

The  Generation  of  H-drocvanic  Acid 
Gas  in  Fumigation  bv  Portable  Ma- 
chines. 


CIRCULARS 
No. 
140. 


The  Practical  Application  of  Imnroved 
Methods  of  Fermentation  in  Califor- 
nia Wineries  during  1913   and  1914 

141.  Standard   Insecticides   and   Fungicides 

versus  Secret  Preparations. 

142.  Practical  and  Inexpensive  Poultry  Ap 

pliances. 

143.  Control    of    Grasshoppers    in    Imperia 

Valley. 

144.  Oidium  or  Powderv  Mildew  of  the  Vine 

145.  Suggestions  to  Poultrymen  concerning 

Chicken  Pox. 

146.  Jellies    and    Marmalades    from    Citrus 

Fruits. 

147.  Tomato   Growing  in  California. 

148.  "Lungworms." 

150.    Round  Worms  in   Poultry. 

151..  Feeding  and  Management  of  Hogs. 

152.  Some  Observations  on  the  Bulk  Hand- 

ling of  Grain  in  California. 

153.  Announcement  of  th°  California   State 

Dairv  Cow  Competition,    1916-18. 

154.  Irrigation    Practice   in   Growing   Small 

Fruits   in   California. 

155.  Bovine  Tuberculosis. 

156.  How  to  Operate  an  Incubator. 

157.  Control  of  the  Pear  Scab. 

158.  Home  and  Farm  Canning. 

159.  Agriculture  in   the   Imperial  Valley. 

160.  Lettuce    Growing    in    California. 

161.  Potatoes  in   California. 

162.  White    Diarrhoea    and    Coccidiosis    of 

Chicks. 

163.  Fundamentals  Affecting  the  Food  Sup- 

plv  of  the  United  States. 

164.  Small  Fruit  Culture  in  California. 

165.  Fundamentals    of    Sugar    Beet    under 

California  Conditions. 


